This invention relates to a microwave assembly comprising microwave components and a stripline-type connecting device for electrically interconnecting these components.
As used in this patent application, the term "component" comprehends both active and passive components and an assembly or sub-assembly of components as well as connectors; and the term "stripline," as applied to a connecting device, denotes a connecting device that comprises a conductor, two metal parts spaced from the conductor and located on opposite sides of the conductor, and solid dielectric interposed between the metal parts and the conductor.
One technique that often has been used for interconnecting, or integrating, microwave components has involved equipping the components with coaxial type connectors (e.g., SMA or the equivalent) and interconnecting these connectors by using mating connectors and some form of coaxial cable connected between the mating connectors. The radio frequency (RF) performance of such an assembly is very good, but this technique is relatively expensive and results in an inefficient use of assembly volume.
Another prior technique involves the use of connectorless (or drop-in) components. These components come in many different forms, the most common of which are those with coaxial terminal structures including a central conductor with a projecting end portion, and those of microstrip form, where a conductive strip mounted on an insulating substrate terminates at one end in a tab-type end portion. Drop-in components are usually integrated into an assembly by soldering or welding the above-described end portions to a microstrip transmission line "motherboard". Typically, this microstrip transmission line motherboard comprises a metal plate defining a ground plane, a dielectric substrate bonded to the metal plate, and a strip conductor bonded to the exposed surface of the substrate.
Typically, the individual components of this latter type assembly and a prototype form of the assembly are evaluated prior to integration either in a coaxial test fixture using removable connectors (for the coaxial-type drop-in components) or in a microstrip-coaxial test fixture (for the microstrip drop-in components).
Although the above-described prior microstrip integration technique has the advantage of reduced assembly volume and weight as compared to the first technique, it has some serious disadvantages. Some of these are: (1) RF performance of the integrated assembly is degraded due to ground discontinuities and RF leakage (e.g., between two parts of a single device or between adjacent lines of two or more devices), (2) as a result, the correlation between the RF performance of the "prototype" and the "integrated" versions of the assembly is typically poor, (3) insertion losses may be relatively high, and (4) the integrated assembly does not lend itself to easy replacement of components since the terminals of the components are welded or soldered to the microstrip transmission line motherboard.